Vehicle

ABSTRACT

An improved vehicle ( 30 ) equipped with a chassis, a pair of driving wheels, a pair of idle wheels and a control group ( 10 ) of the movement of the pair of driving wheels, wherein the group ( 10 ) comprises a differential group equipped with an outer box ( 20 ), which can be activated in rotation by a crown ( 15 ), and an inner box ( 19 ) in which a first and second end of two half-shafts ( 11, 12 ) converge, respectively rigidly connected to two primary toothed gears ( 13, 14 ) connected to each other by means of two secondary toothed gears ( 16, 17 ) rotatingly assembled on a pin ( 18 ) of the inner box ( 19 ) substantially orthogonal to the half-shafts ( 11, 12 ), the group ( 10 ) also comprising selective engagement means ( 21 ) of the inner box ( 19 ) with the outer box ( 20 ), selective blocking means ( 24, 25, 26 ) of the inner box ( 19 ) with respect to the chassis, and selective direct gearing means ( 22, 23, 27, 28 ) of the movement coming from the crown ( 15 ) to one of the two half-shafts ( 11, 12 ), wherein when the inner box ( 19 ) is integral with the outer box ( 20 ) a concordant rotation is transmitted to the pair of wheels and wherein when the selective blocking means ( 24, 25, 26 ) and the direct selective gearing means ( 22, 23, 27, 28 ) are contemporaneously activated, an opposite rotation is transmitted to one wheel with respect to the other, the vehicle also comprising at least one steering group ( 100 ) of the wheels of at least one axle.

The present invention relates to an improved vehicle.

The term “vehicle” refers to common automobiles but also elevator trucks, earth-moving vehicles, off-road and non-off-road telescopic trucks, military vehicles, tractors, air platforms, i.e. all vehicles which, during their normal use, effect maneuvers in which the relative wheels have a steering configuration necessary for allowing a movement, for example straight or curved, of the vehicle itself.

In currently known vehicles, the steering, i.e. the positioning of a particular desired orientation of at least one pair of wheels, is generally controlled mechanically by means of a rack coupling activated by the movement of the steering wheel or hydraulically by means of a hydraulic auxiliary system again controlled by the rotation of the steering wheel.

In particular, the known steering groups act on the wheels of an axle which are constrained to the vehicle by means of structural extensions.

In order to effect a turn, when desired, the presence is currently envisaged of a rigid rod element connected at one end to a steering stem by means of a spherical coupling and at the other end to the wheel-holder group by means of a pin, this being the construction solution of the integrated steering cylinder type mainly used for axles to be installed on off-road vehicles.

At present, therefore, in order to effect a sudden turn, a user exerts a translatory movement, generally, as already mentioned, by means of the steering wheel, to the above stem of the main cylinder which in turn entrains the other rigid rod element situated in series with the previous stem, into movement.

As this rigid rod element, however, is integrally hinged to the wheel-holder supports of the wheels of a common axle, the latter are concordantly put into movement and, in particular, in rotation in the same direction around the relative pins through which they are rotatingly connected to the structural extensions, respecting the geometrical constraints imposed by the steering mechanism selected.

The only turns therefore that a current known vehicle can make through the coupling described above falls within the typologies contemplated by the “Ackermann”-type geometry in which the wheels of a common axle can be oriented towards the same side and corresponds to the turns normally effected in common bend maneuvers.

Unfortunately, however, these known groups have various drawbacks and impose kinematic limits to the vehicle itself on which they are assembled.

In particular they relate to the limited angular excursion granted to the wheel-holder support which is constrained and exclusively limited to the translatory movement of the above stem of the main cylinder.

In other words, unfortunately, the angular excursion of the wheel-holder group around the connection pin with the structural extensions, is limited within a narrow angular range which cannot exceed what is granted and exerted by the translatory movement of the stem driven by the steering wheel or hydraulically activated. Unfortunately the steering mechanism currently used does not allow the limits of the turning radius imposed by the Ackermann steering geometry which prevents the rotation of the whole vehicle with respect to a point inside the ground-support quadrilateral of the same vehicle, to be exceeded.

It is not possible, for example, for present known vehicles to rotate around the centre of their own rigid driving axle, for example the front drive, nor is it possible to effect a rotation with respect to the centre of the vehicle itself for the above-mentioned kinematic reasons of the known steering groups and also because it is not possible for current known vehicles to impose two discordant rotations on a pair of driving wheels of the same axle.

An objective of the present invention is to provide a device capable of solving the above drawbacks of the known art in an extremely simple, economical and particularly functional way.

A further objective is to provide a vehicle which enables greater steering angles to be obtained with respect to those which can currently be reached.

Another objective is to provide a vehicle which enables wide steering angles to be obtained without requiring effort on the part of the user acting on the steering wheel, thus improving the maneuverability of the vehicle in limited spaces.

Yet another objective is to provide a vehicle which allows steering around a point inside the vehicle itself such as, for example, the centre of a rigid front drive axle or with respect to the centre of the vehicle.

An additional objective is to provide a vehicle capable of imposing two discordant rotations on a pair of drive wheels of the same axle.

These objectives according to the present invention are achieved by providing a steering group of the wheels of a vehicle as specified in claim 1.

Further characteristics of the invention are indicated in the subsequent claims.

The characteristics and advantages of an improved vehicle according to the present invention will appear more evident from the following illustrative and non-limiting description, referring to the enclosed schematic drawings, in which:

FIG. 1 is a sectional view of the driving group of the movement of the driving wheels of the vehicle, object of the present invention;

FIG. 2 is a view from above of the steering group of the wheels of an idle axle of the vehicle according to the present invention in a possible straight advance configuration;

FIG. 3 is a view from above of the steering group of the wheels of an idle axle of the vehicle of FIG. 2 in another possible configuration of use according to the classical steering in accordance with the Ackermann steering geometry;

FIG. 4 is a view from above of the steering group of the wheels of an idle axle of the vehicle of FIG. 2 in another possible configuration of use according to a steering in which the rotation of the vehicle is effected around a point positioned on the edge of a side of the ground-support quadrilateral or inside the vehicle, i.e. in the centre of the vehicle itself;

FIG. 5 is a schematic view from above of a vehicle according to the present invention in which the wheels of an axle are positioned according to the geometry of the steering group of FIG. 3;

FIG. 6 is schematic view from above of a vehicle according to the present invention in which the wheels of an axle are positioned according to the geometry of the steering group of FIG. 4; and

FIG. 7 is a schematic view from above in which the wheels of both of the axles are positioned according to the geometry of the steering group of FIG. 4 and in which at least one of the axles is the driving axle and equipped with the steering mechanism 100 object of the present invention.

With reference to FIGS. 5-7, these show an improved vehicle 30 according to the present invention equipped with a control group 10 of the movement of the driving wheels 40, 40′, in a sectional view of an illustrative embodiment in FIG. 1, and two steering groups 100 of the wheels of both axles.

Said vehicle 30 is, like all known common vehicles, equipped with a chassis 35, a pair of driving wheels, indicated in the figures with 40, 40′, and a pair of idle wheels 50, 50′.

As already mentioned, the vehicle 30 is equipped with a control group 10 of the movement of the driving wheels 40, 40′, which comprises, as can be seen in the schematic example represented in FIG. 1, a differential group 20, 19.

In particular, this differential group 20, 19 comprises an outer box 20, which can be activated in rotation by a crown 15 activated in rotation by a motor, and an internal box 19 in which a first and second end of two half-shafts 11, 12 converge, from facing opposite ends.

The relative wheel-holder groups of the driving wheels 40, 40′ are connected to the opposite ends of the two half-shafts 11, 12, those distant from the differential group 20, 19.

Two primary toothed gears 13, 14, which communicate with each other for a possible transmission of the movement between two secondary toothed gears 16, 17, are rigidly respectively connected to the ends of the two half-shafts 11, 12 converging inside the inner box 19 of the differential group 20, 19.

The latter secondary toothed gears 16, 17 are in turn rotatingly assembled on a pin 18 of the inner box 19 which 18 is substantially orthogonal to the two half-shafts 11, 12.

According to the invention, the control group 10 also comprises selective engagement means 21 of the inner box 19 with the outer box 20, selective blocking means 24, 25, 26 of the inner box 19 with respect to the chassis, and direct selective gearing means 22, 23, 27, 28 of the movement coming from the crown 15 to one of the two half-shafts 11, 12.

In particular, according to the invention, when the inner box 19 is integral with the outer box 20 a concordant rotation is transmitted to the pair of driving wheels 40, 40′, whereas when the selective blocking means 24, 25, 26 and the direct selective gearing means 22, 23, 27, 28 are activated, an opposite rotation with respect to the other is transmitted to the same pair of driving wheels 40, 40′.

In particular, according to an embodiment shown in FIG. 1, the selective engagement means 21 of the inner box 19 with respect to the outer box 20 comprise a set of engagement balls 21 interposed between the inner box 19 and the outer box 20.

As can be seen in the same example of FIG. 1, the selective blocking means 24, 25 26 of the inner box 19 with respect to the chassis 35 comprise at least a first moveable piston element 24, at least a first spring element 26, and at least a clutch element 25 connected to the framework of the chassis 35 wherein the at least one piston element 24 can be selectively moved to compress the at least one spring element 26 and disconnect the engagement means 21 of the inner box 19 with respect to the outer box 20 bringing the inner box 19 to the chassis by means of the clutch element 25 if said clutch is “packed” with respect to the bridge framework and consequently to the chassis 35.

In the same preferred embodiment shown, the direct selective gearing means 22, 23, 27, 28 of the movement coming from the crown 15 to one of the two half-shafts 11, 12 comprise at least a second moveable piston element 22, at least one front engagement unit whether it be with straight or helicoidal teeth 23, 28 and at least a second spring element 27, wherein the at least second piston element 22 can be selectively moved to compress the at least second spring element 27 and engage the at least one front engagement group with straight or helicoidal teeth 23, 28.

From what is described above consequently, once the selective blocking means 24, 25, 26 and the direct selective gearing means 22, 23, 27, 28 have been activated, i.e. blocking the inner box 19 with respect to the chassis 35 and imposing a rotation directly on one of the two half-shafts 11, 12, due to the coupling of the primary toothed gears 13, 14 and secondary toothed gears 16, 17, the two driving wheels 40, 40′ are activated in rotation following two opposite rotations.

Consequently, the control group 10 described above according to a preferred embodiment allows the driving wheels 40, 40′ to which it is connected to proceed straight with the same angular rate and to effect common curving maneuvers with different and concordant angular rates, when the boxes 19, 20 of the differential are integral with each other and form a common differential, and also according to the invention, the control group 10 allows the two driving wheels 40, 40′ to rotate with different and discordant angular rates with respect to each other.

Only according to the invention is it consequently possible for the vehicle 30 to effect rotations around its own centre in which the two driving wheels 40, 40′ proceed with discordant angular rates of the angular half-axes 11 and 12 wherein, as in the example of FIG. 7, the right wheel 40 follows the instantaneous trajectory indicated in the figure with F whereas the left wheel 40′ follows the instantaneous trajectory indicated with F′.

In order to effect said rotation around the centre of the vehicle 30 described above, the vehicle also comprises a steering group 100 of the wheels 40, 40′, 50, 50′ of each axle which allows the relative wheels 40, 40′, 50, 50′ to be oriented so as to respect the kinematic constraints imposed by the steering geometry mentioned above and also the steering geometries shown in FIG. 5.

An embodiment example of said steering group 100 of the wheels 40, 40′, 50, 50′ of an axle is shown in FIGS. 2-4 and comprises two structural extensions 111, 111′ which are respectively connected at one end to a relative wheel-holder group 113, 113′ and at another end to a portion 112 rigidly connected, or oscillating, with respect to the vehicle 30.

In particular, the wheel-holder groups 113, 113′ are respectively rotatingly connected to the two structural extensions 111, 111′ around a relative first pin 114, 114′.

According to the invention, the steering group 100 also comprises steering means 101, 101′ of the wheel-holder groups 113, 113′ equipped with two independent telescopic units 115, 117, 115′, 117′ capable of steering the relative wheel-holder groups 113, 113′ having a common axis according to independent steering geometries.

Each telescopic unit 115, 117, 115′, 117′ is rotatingly connected to the relative wheel-holder group 113, 113′ by means of a second pin 116, 116′, and comprises a first sleeve element 115, 115′ and a first rod element 117, 117′ which slides inside the first sleeve element 115, 115′.

The relative independent movement of the first rod element 117, 117′ inside the relative first sleeve element 115, 115′ modifies, independently of the normal steering geometry (FIG. 5), the angular position of the relative wheel-holder group 113, 113′ with respect to the structural extensions 111, 111′ allowing a geometry of the type shown in FIG. 4, to be reached.

Furthermore, each steering group 100 also comprises a main moveable steering stem 120 in a main steering sleeve 121, rigidly constrained to the vehicle, from which it at least partially protrudes laterally with relative ends both equipped with an articulated element 118, 118′.

According to the embodiment shown in FIGS. 2-4, the first sleeve elements 115, 115′ are respectively rotatingly connected to the wheel-holder groups 113, 113′ by means of the above second pins 116, 116′, the first rod elements 117, 117′ are respectively equipped with an end which slides inside the two first sleeve elements 115, 115′ and another end spherically connected to the above articulated elements 118, 118′, on the opposite part, to the main steering stem 120.

According to illustrative embodiments, the movement of the first rod elements 117, 117′ with respect to the first sleeve elements 115, 115′ is hydraulically driven, whereas the movement of the main steering stem 120 is driven by means of specific drives directly connected with the rotation of the steering wheel such as a rack or hydraulic actuator.

In particular, the movement of the first rod elements 117, 117′ with respect to the first sleeve elements 115, 115′ is independent with respect to the movement of the main steering stem 120.

If there is no relative movement between the first rod elements 117, 117′ and the respective first sleeves 115, 115′, the movement of the main steering stem 120 allows the wheel-holder groups 113, 113′ having a common axle to be steered as required, respecting the geometrical constraints imposed on the mechanism by the Ackermann geometry typical of a common bend advancement.

This arrangement is shown in FIG. 3 and allows the vehicle 30 to effect curved trajectories such as that shown in FIG. 5 in which the steering group 100 of an axle, for example the rear axle equipped with idle wheels 50, 50′, imposes, as described above, an Ackermann geometry on the relative wheels whereas the other axle, for example the front axle equipped with driving wheels 40, 40′, respectively imposes a curved geometry on the relative wheels around the instantaneous rotation axis 60 of the vehicle 30.

In particular therefore, common curvature maneuvers which can be effected with the currently known steering devices with an instantaneous rotation centre of the vehicle 30 outside the same vehicle 30, are possible with the object of the present invention.

If, on the other hand, the main steering stem 120 is kept in a blocked position and centered with respect to the centre line of the vehicle 30 and there is a telescopic movement of the two first rod elements 117, 117′ with respect to the relative sleeves 115, 115′ on both the right and left side of the common axle, new angular positions of the wheel-holder groups 113, 113′ are reached, which are suitable for obtaining geometrical constraints that are such as to impose on the vehicle 30 a rotation around a point positioned on the edge of a side of the ground-support quadrilateral or inside the vehicle 30, i.e. the centre of the vehicle itself.

In particular, the instantaneous rotation centre is preferably situated in the centre of the other axle with respect to that in which the wheels are steered as described above, or, by thus steering all the wheels of the two axles, the vehicle 30 can also effect rotations around its own centre.

The example of FIG. 6 shows a vehicle 30 in rotation around an axle and this steering is obtained thanks to the arrangement of the wheels of an axle, for example the rear idle wheels 50, 50′, according to the geometry of FIG. 4, whereas the wheels of the other axle, for example the front axle equipped with driving wheels 40, 40′, are kept fixed parellelly with the development of the vehicle 30, as said front axle is rigid.

FIG. 7 shows a vehicle according to the invention in which the driving wheels 40, 40′ are also arranged according to the geometry of FIG. 4.

In this case, the driving wheels 40, 40′ connected to the common axle are advantageously activated in rotation in discordance with respect to each other by the movement control group 10 according to the present invention previously described by imposing on the vehicle 30, a rotation around its own centre 60 visible in FIG. 7.

These discordant angular positions of the wheel-holder groups 113, 113′ obtained thanks to the movement of the first two rod elements 117, 117′ with respect to the relative sleeves 115, 115′ are represented in FIG. 4, whereas FIGS. 6 and 7 illustrate two vehicles 30 in rotation around the centre of the other axle, and around the centre of the vehicle itself, respectively.

Upon observing the figures in fact, these respectively show three possible different steering configurations of the wheel-holder group 113, 113′ with respect to the relative independent positions of the first rod elements 117, 117′ and main steering stem 120.

FIG. 2 shows a steering group 100 of the wheels of a vehicle 30, object of the present invention, with a zero steering angle in which the stem 120 protrudes symmetrically from the main steering cylinder 121 and the first rod elements 117, 117′ are in such a position, substantially entirely contained, with respect to the relative first sleeves 115, 115′ as to impose a zero steering angle on the two wheel-holder groups 113, 113′.

FIG. 3 shows a steering group 100 of the wheels of a vehicle 30 in which the main steering stem 120 has undergone a total axial translation towards the left side of the centre of the vehicle 30 whereas the two couplings of first rod elements 117, 117′—first sleeves 115, 115′ are in an unaltered position with respect to the previous figure.

In particular, therefore, this configuration shown in FIG. 3 can be obtained starting from that illustrated in FIG. 1 exclusively thanks to the translation of the main steering stem 120 and effects a steering of the Ackermann type shown in FIG. 5.

FIG. 4 shows a steering group 100 of a wheel of a vehicle 30 object of the present invention in which the stem 120 is kept in a blocked and centered position with respect to the centre of the vehicle 30, the same position as FIG. 2, whereas the first rod elements 117, 117′ are brought, for example at run-end, into excursion with respect to the relative first sleeve 115, 115′.

Consequently, in particular, this configuration shown in FIG. 4, can be obtained starting from that shown in FIG. 2 exclusively thanks to the movement of the first rod elements 117, 117′ with respect to the first sleeve elements 115, 115′ and allows the vehicle 30 to effect a rotation around the centre of the other rigid front axle as shown in FIG. 6, or to effect a rotation around the centre of the vehicle 30 if the vehicle 30 envisages both the two steering axles equipped with the steering group 100, object of the present invention, and at least one of the axles comprising the inversion mechanism of the differential, i.e. the movement control group 10.

This latter possibility is schematically shown in FIG. 7.

As can be seen in FIG. 4, the movements of the first rod elements 117, 117′ with respect to the relative first sleeve 115, 115′, preferably selectively driven hydraulically, allow an extra angular excursion of the wheel-holder groups to be obtained, also with the stem 120 in a blocked and centered position.

Thanks to the steering group 100 of the wheels of a vehicle 30 according to the present invention, it is advantageously possible to confer this angular position with a maximum almost transversal opening visible in FIGS. 6, 7 and 4 to the wheel-holder groups 113, 113′ with respect to the relative structural extensions 111, 111′.

This aspect is also advantageous because, as this excursion is independent of the movement of the main steering stem 120 and therefore independent of the rotation of the steering wheel on which the user acts, it allows these extra-excursion configurations to be obtained hydraulically without requiring excessive effort on the part of the user and without jeopardizing the use of the main steering cylinder 121.

The functioning of the device, object of the invention, can be easily understood.

The vehicle 30 according to the present invention is equipped with steering groups 100 of the wheels 40, 40′, 50, 50′ of the two axles and a control group 10 of the movement of the driving wheels 40, 40′.

In particular, these steering groups 100 are equipped with steering means 101, 101′ which comprise for each wheel-holder group 113, 113′, a telescopic unit 115, 117, 115′, 117′ each equipped with a first rod element 117, 117′ which slides inside a relative first sleeve element 115, 115′.

In particular, said at least one telescopic unit 115, 117, 115′, 117′ is interposed between the relative wheel-holder group 113, 113′ and a central portion 112 of the axle integral or oscillating with respect to the vehicle 30, in series with a main steering stem 120 driven by the user by means of the steering wheel or hydraulically.

Thanks to the present invention, the steering of the wheel-holder groups 113, 113′ is also possible independently of the excursion of the main steering stem 120 in effecting steering geometries which allow the wheels to be arranged so as to allow the vehicle 30 to rotate around the centre of the other rigid front axle or around the centre of the vehicle 30 itself.

In this latter case the driving wheels 40, 40′ are advantageously set in rotation by the movement control group 10 of the present invention according to opposite rotations compelling the vehicle 30 to rotate around its own centre.

In particular, consequently, the vehicle 30, by means of the relative steering groups 100, 100′, can orient the wheels as illustrated in FIG. 7 and, by means of the movement control group 10, it can move around its own centre.

It can thus be seen that the improved vehicle according to the present invention achieves the objectives previously indicated.

The improved vehicle of the present invention thus conceived can undergo numerous modifications and variants, all included in the same inventive concept; furthermore all the details can be substituted by technically equivalent elements. In practice, the materials used, as also the dimensions, can vary according to technical requirements. 

1. An improved vehicle (30) equipped with a chassis, at least one pair of driving wheels, at least one pair of idle wheels and a control group (10) of the movement of said pair of driving wheels, wherein said control group (10) comprises a differential group equipped with an outer box (20), which can be activated in rotation by a crown (15), and an inner box (19) in which a first and second end of two half-shafts (11, 12) converge, from facing opposite sides, respectively rigidly connected to two primary toothed gears (13, 14) connected to each other by means of two secondary toothed gears (16, 17) rotatingly assembled on a pin (18) of said inner box (19) substantially orthogonal to said half-shafts (11, 12), said control group (10) also comprising selective engagement means (21) of said inner box (19) with said outer box (20), selective blocking means (24, 25, 26) of said inner box (19) with respect to said chassis, and selective direct gearing means (22, 23, 27, 28) of the movement coming from said crown (15) to one of said two half-shafts (11, 12), wherein when said inner box (19) is integral with said outer box (20) a concordant rotation is transmitted to said pair of wheels and wherein when said selective blocking means (24, 25, 26) and said selective direct gearing means (22, 23, 27, 28) are contemporaneously activated, an opposite rotation is transmitted to one wheel with respect to the other of said pair of driving wheels, said vehicle also comprising at least one steering group (100) of the wheels of at least one axle of said vehicle suitable for respecting the kinematic constraints imposed by the selectionable steering geometries.
 2. The vehicle (30) according to claim 1, characterized in that said selective engagement means (21) of said inner box (19) with said outer box (20) comprise a set of engagement balls (21) interposed between said inner box (19) and said outer box (20).
 3. The vehicle (30) according to claim 1, characterized in that said selective blocking means (24, 25, 26) of said inner box (19) with respect to said chassis comprise at least a first moveable piston element (24), at least a first spring element (26), and at least one clutch element (25) selectively integral with said chassis wherein said at least one piston element (24) can be selectively moved to compress said at least a first spring element (26) and disconnect said selective engagement means (21) of said inner box (19) with said outer box (20) bringing said inner box (19) to said chassis by means of the clutch element (25), said clutch (25) being “packed” with respect to said chassis.
 4. The vehicle (30) according to claim 1, characterized in that said selective direct gearing means (22, 23, 27, 28) of the movement coming from said crown (15) to one of said half-shafts (11, 12) comprise at least a second moveable piston element (22), at least one front engagement unit with straight teeth (23, 28) and at least a second spring element (27), wherein said at least second piston element (22) can be selectively moved to compress said at least second spring element (27) and engage said at least one front engagement group with straight or helicoidal teeth (23, 28).
 5. The vehicle (30) according to claim 1, characterized in that said at least one steering group (100) of the wheels of at least one axle comprises two structural extensions (111, 111′) respectively connected at one end to a wheel-holder group (113, 113′) and at another end to said vehicle 30, said wheel-holder groups (113, 113′) being rotatingly connected to said two structural extensions (111, 111′) around a relative first pin (114, 114′) and said steering group (100) also comprising steering means (101, 101′) of said wheel-holder groups (113, 113′) equipped with two telescopic units (115, 117, 115′, 117′) each equipped with a first sleeve element (115, 115′) and a first rod element (117, 117′) which slides inside said first sleeve element (115, 115′), said telescopic units (115, 117, 115′, 117′) being rotatingly connected to said wheel-holder groups (113, 113′) by means of a second pin (116, 116′) and being suitable for independently modifying the angular position of said wheel-holder groups (113, 113′) with respect to said two structural extensions (111, 111′).
 6. The vehicle (30) according to claim 5, characterized in that said at least one steering group (100) of the wheels of at least one axle also comprises a main moveable steering stem (120) in a main steering sleeve (121), rigidly constrained to said vehicle, said first sleeve elements (115, 115′) being respectively rotatingly connected to said wheel-holder groups (113, 113′) by means of said second pin (116, 116)′, said first rod elements (117, 117′) being respectively equipped with an end which slides inside said first sleeve elements (115, 115′) and another end spherically connected to an articulated element (118, 118′), said main steering stem (120) being provided with two ends which extend from opposite sides of said vehicle (30) partially protruding from said main steering sleeve (121) connected to said articulated elements (118, 118′) in an interface position with said first rod elements (117, 117′).
 7. The vehicle (30) according to claim 5, characterized in that the movement of said first rod elements (117, 117′) with respect to said first sleeve elements (115, 115′) is hydraulically controlled.
 8. The vehicle (30) according to claim 6, characterized in that the movement of said main steering stem (120) is rack or hydraulically controlled and the movement of said first rod elements (117, 117′) with respect to said first sleeve elements (115, 115′) is hydraulically controlled.
 9. The vehicle (30) according to claim 6, characterized in that the movement of said main steering stem (120) and the movement of said first rod elements (117, 117′) with respect to said first sleeve elements (115, 115′) are independent of each other. 